1. Field of the Invention
The present invention relates to a license-management system and method, and more particularly, to a license-management system and method in which access to digital content can be controlled in various manners and a license for the use of digital content can be effectively managed.
2. Description of the Related Art
Digital Rights Management (DRM) is basically for enabling the use of content by a user who has legitimately purchased the content. Initial DRM systems have been designed to allow only a device authorized to access content purchased by the user access the content. However, recent developments in home appliance technology and the advent of ubiquitous environments have raised the necessity of allowing a user to use content with more than one device.
In order to meet this necessity, authorized domains (AD) have been developed. The concept of ADs is characterized by allowing devices belonging to an AD to share content with each other without any restrictions while imposing restrictions on the use of content by devices not belonging to the AD. DRM systems which support ADs include Thomson's SmartRight systems, Open Mobile Alliance (OMA) DRM systems, and IBM's xCP systems.
In the case of the OMA DRM system and the xCP system, a central license server directly manages all domains, as illustrated in FIG. 1. That is, in order for a device to enter a predetermined domain, the device needs to negotiate with a central license server. If the device is allowed to enter the predetermined domain, the device may acquire a domain key to the predetermined domain from the central license server. This is described in detail below.
FIGS. 1 and 2 illustrate related art methods of configuring a network with a plurality of devices.
Specifically, FIG. 1 illustrates the situation when four devices D1, D2, D3, and D4 constitute a network Home_A (12). The network Home_A (12) configures two domains AD_1 and AD_2. The domain AD_1 includes all the devices D1, D2, D3, and D4 in the network Home_A (12), and a domain key DK_1 is shared within the domain AD_1. The domain AD_2 only includes the devices D3 and D4, and a domain key DK_2 is shared within the domain AD_2. The domains AD_1 and AD_2 are differentiated from each other in order to appropriately control access to content according to the purpose of use of the content.
The SmartRight system, unlike the OMA DRM system or the xCP system, can configure its own ADs for a number of devices without the aid of a license server 10.
FIG. 2 illustrates the situation when devices D1, D2, D3, and D4 constitute a network Home_B (14). The network Home_B (14) configures only one domain AD_3 which is constituted by the devices D2, D3, and D4, and a domain key DK_3 is shared within the domain AD_3. The device D1 receives from an external content provider encrypted content which can only be decrypted by the device D1, repackages the content with a license and then provides the content to the devices D2, D3, and D4 in the domain AD_3 so that the content can be reproduced by the devices D2, D3, and D4 in the domain AD_3. Since the device D1 does not know of the domain key DK_3, the device D1 needs help from devices D2, D3, and D4 in the domain AD_3.
An AD-management method of a related art DRM system has the following problems.
From the perspective of domain management, related art domain management methods (such as those of OMA DRM systems or xCP systems), which are generally characterized by a central license server that manages all domains, may result in management overload for a central license server. From the perspective of users, related art domain-management methods may cause problems of privacy violation by allowing a central license server to have all the information regarding devices belonging to a user domain.
From the perspective of content management, related art domain management methods have difficulty flexibly controlling access to content because they involve binding a domain with a single domain key. To address this problem, OMA DRM systems or xCP systems have been designed to allow more than one AD to be provided for a single network. However, it is still difficult for OMA DRM systems or xCP systems to provide sophisticated ways of controlling access to content while reducing the load of central license servers. In addition, SmartRight systems do not provide any functions regarding the control of access to content by individual devices.